package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSeesion{

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration){
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {
        //将要去完成simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if(objects.size() == 1){
            return (T) objects.get(0);
        }else{
            throw  new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public Integer createUser(String statementid, Object... params) throws Exception {
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer i = simpleExecutor.createUser(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public Integer updateUser(String statementid, Object... params) throws Exception {
        Executor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer i = simpleExecutor.updateUser(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public Integer deleteUser(String statementid, Object... params) throws Exception {
        Executor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer i = simpleExecutor.deleteUser(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                //底层都还是去执行JDBC代码

                String methodName = method.getName();
                String ClassName = method.getDeclaringClass().getName();

                String statementId = ClassName + "." + methodName;

                //准备参数2：params：args
                Type genericReturnType = method.getGenericReturnType();
                //判断是否进行了 泛型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }
                MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
                String sql = mappedStatement.getSql();
                if (sql.startsWith("insert")){
                    return createUser(statementId,args);
                }
                if(sql.startsWith("update")){
                    return updateUser(statementId,args);
                }
                if(sql.startsWith("delete")){
                    return deleteUser(statementId,args);
                }
                return selectOne(statementId,args);

            }
        });

        return (T) proxyInstance;
    }
}
